During the past two years this project has developed methods to derive chiasma maps from meiotic observations, gene maps from lod scores, and physical maps from somatic cells, and to integrate all these data efficiently into a chromosome map which gives the correspondence between physical location and genetic map distance. All published data up to the present time and much unpublished data on more than 1665 pairs of loci have been processed for analysis by computer programs that have been thoroughly checked out. In the two terminal years we propose to construct maximum likelihood linkage maps for every chromosome in man, test all unassigned loci for linkage to these groups, refine physical locations by the LRO (likely region of overlap) method, test hypotheses about interference, sex differences, chiasma distributions, and recombinational variability, and publish the analyses, computer programs, and the accumulated data on linkage in man, as a secure base for formal genetics and genetic counseling.